An investigation of nutrient inputs to Lake Pontchartrain via North Shore streams

Study Description

The North Shore Lake Pontchartrain study investigates nutrient
loading in streams draining into Lake Pontchartrain. The North
Shore is rapidly expanding in population and urban development.
Nutrient inputs into the lake from this rapidly-expanding
urban and suburban area have been implicated in
contributing to eutrophication. However, estimates of nutrient
loading remain highly speculative. Initial samples have focused on
one-time, seasonal water-chemistry and algae surveys. However, seasonal,
even monthly, collections of water are not sufficient to characterize
nutrient levels in these urbanizing streams, which are subject to swift,
flashy drainage during rainstorms.

As the Nation develops nutrient criteria for evaluating water quality
in the next few years, real- or near-real-time nitrate data will be
invaluable to researchers and those responsible for making water-resource
management decisions. Nitrates are an important component of nutrient
enrichment of waterbodies, encouraging the growth of algae and aquatic plants,
leading to algae blooms and clogging of waterways with nuisance plant species.
In order to better characterize nutrient levels, we are currently field-testing
an instrument for the continuous measurement of nitrate concentrations on
the Tchefuncte River near Covington. The instrument, installed on a bridge, is
capable of continuously sensing and recording nitrate in the low concentrations
commonly encountered in the environment. Our lead technician, Van Bergeron,
and chief, Dennis Demcheck, completed the first series of tests comparing
the monitor's data to samples collected manually during a rainstorm. It is planned
that the monitor will be linked to a satellite, enabling direct transfer of data
to the Louisiana District office. The goal of this project is to display real-time
nitrate data through the Internet.

The following sites have been sampled in December of 1998,
and March of 1999:

Site Name

Station ID

Bayou Lacombe near Lacombe at US-190

07374587

Tchefuncte River near Covington at US-190

07375050

Bogue Falaya at Covington at US-190

07375170

Tchefuncte River at Madisonville at LA-Hwy 22

07375230

Tangipahoa River at Robert at US-190

07375500

Pass Manchac at Manchac at I-55

07380230

Bayou Liberty at Bonfouca at LA-Hwy 433

301604089504700

Cane Bayou near Mandeville at US-190

302015090001800

Bayou Castine near Mandeville at US-190

302105090022100

Bayou Chinchouba near Mandeville at Causeway Access Rd.

302238090053900

Methods and Analysis

Water was sampled twice in the winter of 1998-1999, according to
methods published in the "Field Guide for Collecting and Processing Stream-water Samples
for the National Water-Quality Assessment Program,
Open File Report 94-455". We also sampled the algae community once
that winter, characterizing both phytoplankton, and woody-debris periphyton.
Methods are described in the "Methods for Collecting Algal Samples as Part of the National
Water-Quality Asssessment Program,
Open File Report 93-409".